The present invention relates to a method for shutting down a drive connected to a matrix converter during a power outage and a device for carrying out the method.
It is desirable in many drive applications, such as lifting devices, to shut down the drive(s) during a power outage in an orderly and reliable manner. With drives having a voltage intermediate circuit converter, it is sufficient to install in the voltage intermediate circuit a suitably sized pulsed resistor which is connected electrically in parallel with the intermediate circuit capacitor. This pulsed resistor includes a series connection of a turn-off semiconductor switch and a resistor. Depending on the braking power of the motor, the average voltage of the resistor is regulated by controllably pulsing the turn-off semiconductor switch so that the power dissipated in the resistor corresponds to the instantaneous braking power of the motor.
Other converter topologies exist beside the “voltage intermediate circuit” converter topology, for example, the “matrix converter” converter topology. A matrix converter of this type is connected to the power line via an optional power line or electromagnetic compatibility filter. This power line filter is implemented, for example, by employing line chokes and commutation capacitors connected to the input terminals of the matrix converter. The commutation capacitors which can be connected in a Delta or Star configuration, are essential for the operation of the matrix converter. However, the chokes in the power lines may optionally be omitted.
Since the matrix converter does not include a voltage intermediate circuit, a conventional pulsed resistor can no longer be used for shutting down a drive when employing a matrix converter. Since certain drive applications require a safe shutdown, matrix converters cannot be used with these drive applications for powering the motors. Accordingly, these particular drive applications cannot employ the converter topology “matrix converter.”
It would therefore be desirable and advantageous to provide an improved device for shutting down a drive during a power outage, which obviates prior art shortcomings and is able to specifically operate with a conventional matrix converter.